On one man-made hill 14 miles from Manhattan's truncated skyline, the work is grim -- but worth it.

"This is not a garbage dump; it's a special place," said Chief of Detectives William Allee of New York City's Fresh Kills landfill, the site where the debris from the World Trade Center has been relocated. "It is sacred ground to all of us. We're doing God's work and I feel honored to be here."

The 'God's work' that Allee is participating in involves sifting through dirt, rock, steel and concrete left from the World Trade Center, in hopes of finding human remains from the Sept. 11 tragedy.

Twenty hours a day, 300 police officers, FBI agents, sanitation workers and construction workers comb through the rubble at a site that was shut down by the city last year and then reopened after the September attacks.

Four months after those attacks, more than 1 million tons of debris have been trucked and barged in for systematic sifting and analysis. When human remains are found, they are put in plastic bags, tagged and sent to the medical examiner's office for DNA typing.

The work has an assembly-line routine. FBI agents and forensic specialists in protective white uniforms and respirators scan the flotsam rolling past on conveyor belts. They hit the "panic button" to interrupt the flow when they spot something important — such as a bit of human remains.

Fresh Kills, its name taken from the Dutch words for fresh stream, opened in 1948 as a "temporary" site. The dump took in 2 billion tons of refuse over its lifetime and was called on again after the tragedy.

Among the 649 victims identified so far, about 50 were identified from remains retrieved at Fresh Kills, said Allee, who is in charge of daily operations. Most of the 3,000 remains are fragmentary; two partial bodies have been recovered there.

At another location, detectives wearing face masks decontaminate personal property to be returned to victims' families. Baskets arranged alphabetically on a long table contain identification cards, credit cards, drivers licenses and other documents.

Hundreds of shoes, books, wallets, pieces of jewelry and clothing are catalogued and shelved. Other debris includes a tennis racket, a stuffed animal and a scooter.

Detective Ed Galanek said he wants to believe the owners lost them while escaping to safety.

"That's the trick we tell ourselves," he said.

Nearby, police experts pry apart the wreckage of a smashed car — one of more than 1,000 in the vast junkyard of vehicles retrieved from the streets around the Twin Towers.

Cars, taxicabs, police cruisers and ambulances are stacked two and three deep. Not far away are some 90 ladder trucks and fire engines — scorched and battered monuments to the 343 firefighters killed that day.

Many of the firetrucks have had their nameplates removed, some by firefighters seeking mementoes of fallen comrades for display in the firehouse. One ladder company that lost seven men salvaged the nameplate from its mangled truck and bolted it onto a replacement.

The devastation of the trade center was so vast that almost no furniture from within the towers survived. "In four months here I have yet to see a desk, a chair or a filing cabinet," Allee said.

A few items stand out — such as the broken remains of a bronze statue by Auguste Rodin. The work had been in the offices of Cantor Fitzgerald, a brokerage that lost hundreds of employees.

Richard Marx, an FBI agent who leads a contingent of about 30 agents, declined to say whether any evidence related to the hijackers had been recovered.

But he said there still was a remote chance that the so-called "black boxes" — the cockpit voice recorders and flight data recorders — might be found.

To that end, intact examples of the orange-painted devices and a pair of smashed recorders from a previous crash were on display — just in case workers find similar devices in the wreckage.

"We won't know until we're through with all this what we've got here," Marx said. "This is the biggest crime scene in history."

The Associated Press contributed to this report.